1. Field of the Invention
The present invention relates to a method of obtaining a crystalline semiconductor used for thin film devices such as a thin film insulated gate type field effect transistor (thin film transistor or TFT).
2. Description of the Related Art
Conventionally, a crystalline semiconductor thin film used for thin film devices such as a thin film insulated gate type field effect transistor (TFT) has been fabricated by crystallizing an amorphous silicon film formed by a plasma CVD method or thermal CVD method at a temperature of more than 600.degree. C. in an apparatus such as an electric furnace.
This conventional method, however, has had various problems. The biggest problem has been that it is difficult to obtain a good product because the crystalline silicon film obtained is polycrystal and there is difficultly in controlling its grain boundary, and its reliability and yield is not so high because of its dispersion characteristic. That is, because the silicon crystals obtained by conventional heat treatment grow totally at random, it has been almost impossible to control the direction of its crystal growth.
Accordingly, it is an object of the present invention to solve the aforementioned problems by providing a method for controlling the growth of the crystal.